A key challenge in improving the care of patients with a variety of pulmonary diseases is to help them make choices that best promote their underlying values when faced with multiple reasonable diagnostic or therapeutic options. Unfortunately, patients and their surrogate decision makers are often diverted from making such optimal choices by the foibles of normal human decision psychology. For example, a former smoker with a solitary pulmonary nodule that has been stable on repeated computed tomography may nonetheless choose to have it biopsied because he fears feeling regret if he chooses surveillance and later finds that it is malignant. This may be true even if patients like him are i fact more likely to regret decisions to pursue biopsy, due to the avoidable risks, burdens, and costs of this approach when the results turn out to be normal. Such anticipated regret - that is, the fear among patients or their surrogate decision makers that they will later compare the actual outcomes with better outcomes that might have happened if they had made an alternative choice - may influence a broad range of decisions made by patients with pulmonary diseases and their surrogates. This may deter optimal decision making, as the decision maker's estimation of the likelihood of regret may be inaccurate or may unduly distract decision makers from more important elements of the decision. However, the effects of such regret might also be harnessed, such that providing patients or surrogates with data on decision regret may help them focus their attention on the outcomes most relevant to them. Guided by this hypothesis, I seek to construct a conceptual framework for how patients with lung disease and their surrogate decision makers think about the future at the time of decision making, and to evaluate the specific effects of decision regret information on the treatment selections and decision process quality of such patients and their surrogates. To accomplish these goals, I will conduct two studies to explore regret among patients with pulmonary disease and potential surrogates recruited from outpatient settings at an academic medical center. First, I will produce the conceptual framework by conducting and analyzing vignette- based semi-structured interviews among patients with pulmonary diseases and their potential surrogates. Second, I will conduct a randomized factorial experiment in which participants consider medically relevant hypothetical situations, and choose between two management options described as being equally appropriate but in which the odds and severity of anticipated regret vary. Semi-structured interviews will elicit descriptions of the decision making process, preferences regarding information-seeking about outcomes of treatment decisions, consideration of future counterfactuals at the time of decision making, the relative proximity of the outcomes considered, and the concept of regret as a factor in decision making. Informed by these qualitative data, the subsequent randomized experiment will determine the specific influence of providing manipulated regret data for each option, and measure not only the choices made but the quality of the decision-making process. This project will provide essential preliminary data for a planned NIH K23 Career Development Award that would (1) collect real decision regret data following actual choices by similar patients with pulmonary diseases, (2) develop a decision aid that incorporates decision regret data that is understandable for patients and their surrogates, and (3) test the effectiveness of this enhanced decision aid in real pulmonary practice.